Abstract

The x-ray stability of photodiodes made of poly(9,9-di--octylfluorene-co-benzothiadiazole):perylene diimide, poly[2,7-(9,9-di--octylfluorene)-co-(1,4-phenylene-[(4-sec-butylphenyl)imino]-1,4-phenylene)]:perylene diimide and poly(3-hexylthiophene):([6,6]-phenylC61-butyric acid methyl ester) (P3HT:PCBM) blends has been examined up to lifetime doses equivalent to those used in medicalx-ray digital imaging applications. Dark currents and external quantum efficiencies (EQEs) are not significantly affected after exposure to . Only in the case of P3HT:PCBM is a significant loss in EQE (17% of the initial value) observed. Possible reasons for the observed changes are proposed. When a scintillation layer is attached to the devices, a linear dependence of the photocurrent on the x-ray dose rate is observed for the three material systems.

Received 15 October 2007Accepted 11 December 2007Published online 16 January 2008

Acknowledgments:

The authors would like to thank Max-Planck Institute for Polymer Research in Mainz for the purification of the PDI compound, Cambridge Display Technology and Merck Chemicals for providing the polymers used in this study, and the EPSRC for funding through the Next Generation Electrophotonics program Grant No. EP/C540336.

Abstract

The x-ray stability of photodiodes made of poly(9,9-di--octylfluorene-co-benzothiadiazole):perylene diimide, poly[2,7-(9,9-di--octylfluorene)-co-(1,4-phenylene-[(4-sec-butylphenyl)imino]-1,4-phenylene)]:perylene diimide and poly(3-hexylthiophene):([6,6]-phenylC61-butyric acid methyl ester) (P3HT:PCBM) blends has been examined up to lifetime doses equivalent to those used in medicalx-ray digital imaging applications. Dark currents and external quantum efficiencies (EQEs) are not significantly affected after exposure to . Only in the case of P3HT:PCBM is a significant loss in EQE (17% of the initial value) observed. Possible reasons for the observed changes are proposed. When a scintillation layer is attached to the devices, a linear dependence of the photocurrent on the x-ray dose rate is observed for the three material systems.

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X-ray stability and response of polymeric photodiodes for imaging applications